In the related art, for a seat having a seat back and a seat cushion, especially, for a seat for vehicle use, a seat back frame is formed in a sheet (panel) shape. A peripheral edge portion of the seat back frame is wound up into continuous pipe shape (pipe shape) by a curling processing of the peripheral edge portion. An example is disclosed in Japanese Utility Model Registration No. 2602770 (hereinafter “Patent Reference 1”).
The connecting structure between the seat back frame and seat cushion frame is not disclosed in Patent Reference 1. By means of a pair of left/right connecting brackets set along the outer side surface of the seat back frame and the seat cushion frame, the frames are connected to each other. However, for such a connecting structure, the connecting bracket is positioned on the side of the seat back frame and the seat cushion frame, such that the pads and leg members are restricted by the connecting bracket, and other installed parts installed on the seat back frame and seat cushion frame.